ch18_4字节不含正负符号的乘法运算.asm

来自「51单片机基础篇 对于有一定基础的人看看 包含书中所以的源代码」· 汇编 代码 · 共 23 行

     ;FUNCTION NAME: MUL_4BYTE
     ;FUNCTION: UNSIGNED 4 BYTE MULTIPLY
     ;(07H)(06H)(05H)(04H)=(07H)(06H)(05H)(04H)X(0FH)(0EH)(0DH)(0CH)
     ;WORKING AREA DATA MEMORY:(0BH),(0AH),(09H),(08H)
     ;
     MUL_4BYTE
           	LCALL	CLEAR_INTERNAL_DATA_MEMORY
           	MOV  	R3,#33 		;SHIFT COUNT
           	CLR  	C
     $1     	MOV  	R1,#0BH
           	MOV  	R2,#08H
     $2    	MOV  	A,@R1
           	RRC  	A
           	MOV  	@R1,A
           	DEC  	R1
           	DJNZ 	R2,$2
           	JNC  	$3
           	CLR   	C
           	MOV   	R0,#08H
           	LCALL	DATA_ADD_4BYTE
     $3   	DJNZ  	R3,$1
           	RET
     ;